This reverts commit fd0554ba.

Flutter's `moreOrLessEquals` has a few advantages over `closeTo` from
the `matcher` package:

   * It emits the epsilon value in the test result on failure.
   * It uses a named parameter for epsilon, which improves readability
     at the call site.
   * It has a reasonable default for epsilon in cases where something
     more specific isn't required.

Using it also has the nice property that it aids in its own discovery
when when people go looking for such functionality in new tests.

This change also includes a couple unrelated whitespace formatting cleanups.

Updated references to the old button classes to the new ones in comments and documentation for tests in the material and cupertino libraries. (#62164)

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

This reverts commit 28f2c96a.

* Add ButtonBar.overflowButtonSpacing

* Add AlertDialog overflow button spacing functionality

Revert "AlertDialog.actionsOverflowButtonSpacing and ButtonBar.overflowButtonSpacing (#50609)" (#50674)

* Add ButtonBar.overflowButtonSpacing

* Add AlertDialog overflow button spacing functionality

* Implement AlertDialog.actionsPadding and AlertDialog.buttonPadding

* Add AlertDialog.scrollable

* Add deprecation notice

* Ignore deprecation warning in dialog.dart with TODO

* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

* Wrap alert dialog title and content in single child scroll view

* Scrollable alert dialog title and content tests

* Remove unnecessary comment

* Fix mainAxisSize and crossAxisAlignment issue

* Re-enable const

* Fix bug, add regression test.

* remove unnecessary space

* fix indentof statements in BlockFunctionBody

* fix indentof statements in BlockFunctionBody in tests

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

* Themable elevation on dialogs.

* AlertDialogs Title/Content text styles

* Themable elevation on dialogs.

AlertDialogs Title/Content text styles

* finish merging change

* fixing tests

* Docs fixes

* Change const to final to fix analyzer errors

* Fix analyzer errors

* Remove dart:ui import

* Hans Comments

* Themable elevation on dialogs.

* Added `BackgroundColor` in widget + theme

* Addressing Comments

* Fix test name

* Add debugFillProperties test

* [Material] Add custom shape parameter for Dialogs.

* [Material] Add custom shape parameter for Dialogs.

* Address Hans' first round comments.

* Address Hans' first round comments.

* Address Hans' Second round comments.

* Refactor of cupertino/material/widgets app

* update docs 

* Update tests for const

This reverts commit 61cf946b.